Hello again, dear readers!
I don't have so much time to give to this project, but PiWeather is still moving forward!
The first prototype only had a DS18B20 temperature sensor, and was working on a breadboard, so the next logical step was to design and realize a first PCB for the project. I also moved from the DS18B20 to the DHT22 sensor because it gives both temperature and humidity, and is pretty accurate. I added to that a pressure sensor : the BMP085, sometimes referred to as GY 65 on eBay! This would give my sensor unit the ability to read pressure, temperature and humidity. That's a good start !
I used EAGLE to design the schematics and the PCB :
We made the PCB ourselves like we did for our old quadcopter flight controller shield. It is pretty hard to get good results with homemade PCBs, and the tracks have to be very big if you want to be sure there won't be any problems. We got a working PCB on which we soldered the components, and it succesfully worked, powered by two AA cells!
I am pretty happy with this PCB as it works great, but it obviously has drawbacks:
- PCB making is the worst. It never works as you want, there always is a problem, some tracks are too thin, some are too thick, you have to carefully check for possible shorts...
- There is no protection against oxydation. Of course you can by some sprays for that, but I don't know if that would work great for an outdoor sensor.
- The minimum track width is too big to make something small and reliable
- It's very, very ugly 😀
So I started to look for inexpensive solutions for my PCB to get produced in a "professional" way. And I found exactly what I wanted on Seeedstudio.com .They offer a very cheap PCB service starting at 9.99$ for 5 PCBs of max 5cm x 5cm. Perfect!
Seeedstudio provides you design rule files for EAGLE, so you can see directly if your design will respect their process. I designed a new 2 layer PCB that Seedstudio produced and sent to me in a few days.
I was blown away by the quality of the boards 😀
The v0.2 finally took life and is ready for duty !
In the next weeks we'll try to build the first outdoor sensor, which will be solar powered. Then we'll probably deploy the website hosting the data gathered by the numerous PiWeather stations 😀
Update 25/10/14 : The schematics are on github : https://github.com/psykhi/PiWeatherEAGLE
I also created a Raspberry Pi shield in order to plug the nRF24L01+ 🙂
I will write an article about it!